Quintessence International, 09/1992

This article describes a simple but effective method of bleaching single vital discolored teeth. The patient applies a viscous 10% carbamide peroxide gel in a plastic mouthguard designed to confine the gel only to the discolored tooth. This method has been effective for lightening vital teeth with calcified pulpal spaces.

The aim of this study on latex dental gloves was to establis whether there is any relationship between faults that are detected by filling with water and the entry of liquid into the gloves during use. Twenty-four gloves of different sizes were examined. Large and small holes randomly distributed on the index, middle, and ring fingers, were made in the gloves. The gloves were filled with water and squeezed to detect the amount of water escaping. A mass spectrophotometer was used with the same gloves to quantify the entry of an aqueous solution of potassium bichromate during work. The filling method was effective for revealing all faults in gloves, but it was not able to determine whether there would be fluid entry through the holes during work. While the size of the holes was not predictive for the amount of liquid entering the glove, adherence of the glove to the hand was. Holes of the same size allowed a greater entry of contaminated liquid in adherent gloves than in looser ones.

This in vitro study compared the marginal adaptation of enamel-bonded mesio-occlusodistal composite resin restorations placed using two different insertion techniques (one-step and two-step) and three different curing techniques (occlusal using opaque matrix and wedge systems and interproximal using transparent matrix systems and either transparent, nonreflecting, or transparent, laterally reflecting wedges). The micromorphology of the enamel-restoration interface and the marginal seal were evaluated after the restorations were exposed to mechanical and thermal stresses. Although the difference was not statistically significant, the marginal quality of the restorations placed with the two-step technique was better than that of the restorations placed with the one-step technique. The restorations cured from the interproxi mal direction had significantly better marginal adaptation than did restorations cured only from the occlusal direction. The quality among the groups of interproximally cured restorations was not significantly different, because all the restorative techniques that were evaluated resulted in generally poor marginal quality.

In the future, dentists will more frequently encounter patients who have dental implants. To use radiographs to identify implants that were previously inserted by other dentists, dentists have to be familiar with the detailed morphology of different products and types of fixtures as well as with the principles for formation of their radiographic images. In the present study, radiographic images of ten common dental implants were analyzed. Images varied with viewing angles. The influences of surface structures, such as threads, cuts, holes, perforations, and flutes, are demonstrated.

The antiplaque potential of zinc salts has been previously demonstrated. The purpose of the present investigation was to establish the effect of zinc chloride dentifrices on plaque growth and on the concentration of zinc in saliva and plaque. Ainc levels in saliva and plaque were measured by atomic absorption spectrophotometry. Elevated zinc levels were observed in saliva and in plaque for 1 hour after contact with a zinc chloride dentifrice. Increased concentrations of zinc were also observed in plaque residue. Further analysis of data showed that subjects with high rates of plaque growth benefited more from the zinc dentifrices than did those with low rates of plaque growth.

In part I of this study, it was reported that high shear bon strengths to dentin were obtained by using a particular dentin-enamel bonding system on wet dentin. Because it would be difficult to dry the enamel without drying the dentin, an investigation was undertaken to determine if the treatment of enaemel surfaces with various phosphoric acid concentrations would be successful on wet enamel using the same bonding system. It was discovered that the bond strengths to etched and wet enamel using a particular dentin-enamel bonding system were equal to or higher than bond strengths to etched and dry enamel.

This study evaluated the relationship of polymerization shrinkage during composite resin veneer placement to direction of the polymerization light source. Fifty maxillary permanent incisors were obtained and divided into five groups of ten. Groups I and II had preparations placed in enamel. Groups III, IV, and V had preparations place d in dentin. In groups I and III, an unfilled bonding resin was placed and polymerized from the facial aspect, followed by placement and polymerization of a hybrid composite resin. Groups II and IV were initially polymerized from the lingual direction. In group V, the unfilled resin and hybrid composite resin were polymerized simultaneously from the facial aspect. Statistical analysis indicated that there was significantly less axial microgap formation during lingual polymerization when the preparation remained in dentin, but demonstrated that there ws no statistically significant difference when the preparation remained in enamel.

The tensile bond strength to dentin was measured for three glass-ionomer cement and composite resin combinations: two light-curing glass-ionomer cements 9Vitrebond and XR-Ionomer) and one traditional glass-ionomer cement (Ketac-Bond), two adhesive systems (Scotchbond, and XR-Bonding System), and a corresponding composite resin. The bond strength of this sandwich was also compared with that of the same cements used in bulk. Vitrebond showed a significantly higher bond strength in bulk than did the other two cements. Of the sandwiches, the XR-Ionomer and XR-Bond combination showed a bond strength significantly higher than that of the Vitrebond and Scotchbond or Ketac-Bond and Scotchbond combination. The f racture of the bond was mainly adhesive for Vitrebond, cohesive for XR-Ionomer when used in bulk and adhesive-cohesive when used in a sandwich, and cohesive for Ketac-Bond.

The purpose of this study was to compare the shear bond strength to composite resin of a light-curing glass-ionomer ce ment with that of various chemically curing glass-ionomer cements. Light-cured composite resin cylinders were bonded to cylindrical glass-ionomer substrates after etching for 30 seconds with 37% phosphoric acid. Specimens were maintained in distilled water for 7 days and then thermocycled in water baths. One group of light-cured glass-ionomer cement substrates was not etched. The interfacial bond strength of these specimens was measured in shear. Cement shear strength was also evaluated. Statistical analysis showed the light-curing cement to have a significantly higher bond strength to composite resin than any of the chemically curing cements tested.